Canon EOS 5D Mark III Instruction Manual (en)

 Fine Adjustment of AF’s Point of FocusN
Enter the serial number.
Turn the <5> dial to select the digit, 
then press <
0> to display <r>.
Turn the <5> dial to enter the 
number, then press <
After entering all the digits, turn the 
<5> dial to select [OK], then press 
About the Lens Serial Number
In step 3, if “ * ” appears in front of the 10-digit lens serial 
number, you cannot register several copies of the same lens 
model. Even if you enter the serial number, “ * ” will remain 
The lens serial number on the lens may differ from the serial 
number displayed on the screen in step 3. This is not a defect.
If the lens serial number is eleven digits or longer, enter only the last 
ten digits.
If the lens serial number includes letters, enter only the numbers in 
step 3.
The location of the serial number differs depending on the lens.
Some lenses may not have a serial number inscribed. To register a 
lens that has no serial number inscribed, enter any serial number in 
step 3.
If [Adjust by lens] is selected and an Extender is used, the adjustment 
will be registered for the lens and Extender combination.
If 40 lenses have already been registered, a message will appear. After 
you select a lens whose registration is to be erased (overwritten), you 
can register another lens.